Java Hash类 取值方式

Map<String, String> map = new HashMap<String, String>();
map.put("1", "11");
map.put("2", "22");

System.out.println("里面的值有：");
Collection<String> connection = map.values();
Iterator<String> iterator = connection.iterator();
while (iterator.hasNext()) {
System.out.println(iterator.next() + "..");
}

System.out.println("里面的键有：");
Set<String> key = map.keySet();
for (String string : key) {
System.out.println(string);
}

System.out.println("里面的键值对是：");
Set<Map.Entry<String, String>> set = map.entrySet();
Iterator<Map.Entry<String, String>> iterator2 = set.iterator();
while (iterator2.hasNext()) {
Map.Entry<String, String> entry = iterator2.next();
System.out.println("键是：" + entry.getKey() + "值是：" + entry.getValue());
}

public static void main(String[] args) {
Set<String> set = new HashSet<String>();
set.add("one");
set.add("two");
set.add("three");

Iterator it = set.iterator();

while(it.hasNext()){
System.out.println(it.next());
}
}